Screw-cutting attachment for machine tools having a reversible working spindle



Nov. 15, 1955 2,723,406

F. ANGST SCREW-CUTTING ATTACHMENT FOR MACHINE TOOLS HAVING A REVERSIBLEWORKING SPINDLE Filed Sept. 13 1951 7 6 1\ 4 4547/11126 $27 2 3 45 46 42F/GZ nitehtates Patent SCREW CUTTING' ATTACHMENT FOR, MACHINE TOOLSHAVING A REVERSIBIJE' WORKING SPINDLE Glaims:priority-aapplicatiomSwitzerland;

September 22,, 19.50:.

3 Claims. (Cl. 10129),

My invention; relates. to--an improved. screw cutting ate tachment. formachine tools. in which: the direction of rotation of. the workingspindlefis reversiblei The-main:

. object. of my inventionsisitonaiford-zan accurateand simpleadjustment.of. the desired length of thread. on: the workpiece, a. frictionless.-andshock-free idling of the: cutter: whenthe operation. of. cutting, ortapping has been comipleted,.'and an automatic. complete engagement? Ofithe: clutch after. the: directiontofl rotation of the machine-tool:spindle-headhas-beenreversedz.

I attainthese and. related ohjectsbythe screw-cutting: attachmentshown,-. by; way of. example; irt th'eaccompanying drawing in which-Eiglshowsa section: ontthe. line II.-of Fig. 3through the attachment atthe start of the cutting opera-horn.

Fig.- 2. depicts-a. similar; section,-. but.in.idl.ing,position;,

Fig... 3. is. a-. crossrsection: on the? line I-IIILL of; Fig; 2, and.i

Figs. 4-, and 5 illustrate verticals part sections. througha detailofthe attachment at-thebeginningand; on. com.-

pletionof. the cutting operation respectively. 35

In the drawing, 1 is an-druml-ike, externally threaded housing of.which. the sleeveextensiom 1a. serves for settingv the mechanism,. forexample, in the tailstocle. of a lathe or in the spindleheadlofadrillingmachine. On the. free: end face. of. housing. 1, is mounted. ascrew. cap- 2 which. is provided with. anpackingA and-ex-ternal threads.for securing; a. protective tube.v 3.-en-veloping, the housing 1Between. cap. 2. and. said. free end of. the housing 1t isclampedabearing, collar-50f which the. internal surface at: is. destinedlfor.co-aetion wit-l1-thencylindrical'surface 45 Sofa hollow. shank]... The.front endpor-tiomofithe. latter is provided with an outwardly-divergingconical, inside face 8 against which is forced a corresponding conicalchuck 9 througlrascrew cap 103which is mounted on the externalthreadsof. shank 7. 50

The inner end portion of'shank 7 has a cylindrical bearing face -llwhichbearson the-cylindrical inside wa11"12 of. housing 1- in an axiallymovable and rotatable relation. The: outside wallof shank- 7 isconicallyshaped between the hearing facesG-and 1-1-, ashouldenlwbeingprovided on the inner end portion of. shank 7; A- spring 15 at one endbears onthe collar 5 and its other end, on said shoulder'-14 of shank 7:In the shank 7 is secured' a central stud 16 having a threaded frontportion 17, the said stud being inserted through the rear portion ofshank 7 and 6 located in such position by a grub screw 18. Two pins 19(of which only one is shown) project into the hollow space of shank 7and are engaged in a rear cross-groove 20, of an inset 21. In a frontcross-groove 22 of inset 21 is engaged the square end portion of thestem 24 of a 65 die or tap 25.

On the inner end face of shank 7 are provided a plurality ofcircularly-disposed conical recesses 26 which, together withcorresponding recesses 27 in the end face of a disclike first clutchelement 28, form cages for driving balls 29. The first clutch element 28has sectorlike 2. claws 30 adapted for co-actiontwitlt therecessesdisposed between corresponding claws 31 on theadjacentface ofasecond. clutch. element. 32. The central studs 16. on which the two.clutch elements 28,. 32' are rotatably mounted, comprises-an integralcollar 33 which separates thev two: clutch. elements and forms theabutment. of. a conical. spring. 34' which. is mounted ottthe element28.- Adjacenttosaid. collar 33;. the stud; 16 has a central pon tion 35whichis formed as a double. cone of which the. extension is againcylindrical and serves as: hearing, for the. clutchrelement. 32;

The outside cone portion of the central part 35 has twoaxialr grooves 36and. coi-acts with balls 37 which, aredisposed-in radial bores 38 of,the clutchelement32r Theballs 37. are loaded by springs 39-whichaaredispjosed in. the bores 38 and supported ongrub screws 40; The

free cyl ndrical'end portion of .stud lfir'lS providedzwith a. stop.screw 41 of which the. head is of larger diameter than the? cylindricalvstud end.

Two rollers. 4-3 (one only being visible in Figs; 1 and 2') are pivoted.on threaded pins 42 tot-he clutch element 32 andare movable inrecessess44 of the housing 1 (Figs. 4, 5). A. setcollar 45 which is.axially movableon theexternal threads- 0f housing 1: and of .which theend faceadjacent the'clutch element32 hasrecesses' 46, serves as: astop'for the rollers 43 and. for setting. the desired length of. threadto' be cut in the workpiece. In. order torpermit to positively locate.the collar 45 with respect. to'its axial positionfor certainlengths ofthread to:be1cut,,the collar 45 is: provided: with set screws: 47 whichare engageable in: longitudinal; grooves! 48 of the: housing; (Fig;4-)1.

Mod-e ofoperation It. is assumed that the sleeve extensionlazis-setinthe: tailstock of a lathe provided with a movablespindle head, and thatthe. set collar' 45 is set. on-theihousingtlin accordance' with thelength of the external righthan'ded thread: to be; cut. and: is fixedby. means of. the set. screw 47 in the groove 48, for example asshownirtFig. 4. The mechanism is supposed tobe in the position shown in Fig.1.

The workpiece, having; been clamped. in the. lathe spindle head: afterthelathe has been put inFoperation, is rotating counterclockwise. Thetool 250i theattachment. clamped in the tailstozckis. movedup 1 to the:workpiece: and pressed against thesame during approximately a revolutionthereof, i.. e. until the. workpiece, has: been-positively engaged bythe tool. The toolvia the shank 7, the-em gaged clutch. 28/32.. and tthe rollers 43. which, abut: against the. respective. edge. of: therecess 44, through: the sta:-- tionary housing L is. secnredragainstrotation. Theshank 7 in. the.initialpositiomshown. in Fig.. 1'. is.guided attwo. points bythe co-acting.surfaces.5a,,.6-and.12,,111

When the tool 25.engages.the workpiece,.the.lattentends. to drive. theshank.7! thereby causing, the clutch, element 28,..onacco1mt of thewedge: actiontoftheballs 29.ii1,the. cages 27/26; to be raised againstthe action o, pring,.34. from. the. adjacent .faceof shank 7untiliticontacts. the collar 33, thereby afl ording play to the parts7'and28.

During the cutting operation, the tool 25 and the parts 7, 16 and 28, 32connected thereto are pulled to the left in Fig. 1 (see arrow P) inaccordance to the screw pitch, the rollers 43 moving along therespective edge of the recesses 44 (Fig. 4) until contacting the setcollar 45. On continued rotation of the workpiece, the clutch element 28is further pulled to the left through a distance defined by the heightof the claws 30, until the clutch elements 28, 32 are disengaged fromeach other. The clutch element 28, which now is freely rotatable,through spring 34 is pressed against the endface of the freely rotatableshank 7 and the two clutch elements 28, 32 thus are separated from eachother by the clearance a (Fig. l)

Patented. Nov.. 15,- 1955 & present between the parts 7 and 28 duringthe cutting operation. Such arrangement ensures, upon completion of thecutting operation, a frictionless and shockfree idling run of the tooland excludes the risk of any undesired clutch engagement as may becaused, for example, by vibrations.

Concurrently with the disengagement of the clutch portions 32 and 28,the cone portion 35 is additionally tensioned by virtue of the balls 37engaging the portion 35. The balls 37 then run freely over the grooves36 on the rotating cone face. The proper length of thread to be cut thusis defined by the total axial movement of the tool 25 and is greaterthan the setting length of the collar 45, the difierence being given bythe height of the clutch claws and the path of movement defined bypressing of the tool.

In order to release the threaded work piece, the direction of rotationof the lathe spindle head is reversed so that the workpiece now rotatesclockwise and, thus, also the shank 7, the clutch element 28 and thestud 16. The balls 37 which during the forward movement of the tool 25have been dislodged through the conical portion 35 from the narrowestpoint thereof, slide on the cone face and will be engaged in thelongitudinal grooves 36 during the rotation of stud 16. Such engagementgives origin to a temporary engagement of the parts 16 and 32 and, sincethe stud 16 now rotates in direction of the arrow R (Fig. to a rotationof the clutch element 32 until the rollers 43 thereof abut against theopposite edge of the recesses 44. As soon as, on further rotation of theclutch part 28, the claws 30, 31 are turned in such manner relatively toeach other that they are capable of interengagement, the balls 37 underthe action of the springs 39 slide back to the narrowest point of cone35, since the rollers 43 and thus the clutch element 32 through therecess 46 of collar 45 are permitted to move forward further. Therecesses 46 are selected of such size that, owing to said movement ofthe clutch element 32, the latter again is engaged to the element 28. Byvirtue of such arrangement, the clutch is automatically and positivelythrown in after the direction of rotation of the lathe spindle head hasbeen reversed. The tool 25 thus is prevented through the engaged clutchfrom further following the rotation; the tool therefore is disengagedfrom the workpiece and, together with the parts coupled thereto, is slidback in accordance with the screw pitch.

When the tool 25 is in its advanced position (Fig. 2), the stop screw 41in stud 16 prevents the clutch elements from being so moved rearwardly,for example on account of blows or other vibration, that the balls 37would be situated on the cylindrical end portion of stud 16 and that thecone 35 and its grooves 36 would become ineffective.

It will be noted yet that, owing to the conical configuration of theouter surface 13 of shank 7, which surface adjoins the surface 6thereof, the shank 7 is no longer guided by the collar 5 when the shank7 has moved forward. In this position, therefore, the shank 7 also bearsat only two points, namely through the tool 25 on the workpiece andthrough the face 11 on the housing 1. When the workpiece is runninguntrue, the tool 25 thus may oscillate.

By turning the collar 45 so that the recess 46 adjoins one or the otherlongitudinal edge of recess 44, righthanded or left-handed threads maybe cut, as desired.

By inserting a suitable front part, in place of shank 7, dies may be setinto the attachment.

What I claim as new and desire to secure by Letters Patent, is:

1. In a screw threading attachment for machine tools having a reversibleworking spindle, the improvement comprising a housing having a shankreciprocably mounted therein and said housing adapted to be connected tosaid spindle, a stud having a conical portion therein secured to thecenter of said shank, said conical portion having an axial groovetherein, a plurality of spring loaded balls engaging said conicalportion and adapted to coact with said groove, a clutch mounted on saidstud and adapted to prevent rotation of said shank when cutting threads,said clutch comprising a first clutch element in which said balls aremounted and having an abutment roller for limiting the work stroke ofsaid shank, a second, spring loaded clutch element adapted to engagesaid first clutch element, said housing having a recess therein, saidabutment roller being axially and rotatably movable within said recess,a set collar movably carried by said housing and engaging said abutmentroller when said shank has completed its working stroke to separate saidclutch elements, said collar being provided with a recess, said firstclutch element on reversal of the direction of rotation of the workingspindle being partly rotated by engagement of the balls in thhe groovein the conical portion of said stud thereby engaging the abutment rollerin the collar recess for permitting axial movement of said first clutchelement for interengaging said first and second clutch elements.

2. The combination of claim 1, said second clutch element having drivingballs coacting with the shank to provide axial play between said shankand said second element when said clutch elements are engaged, andeliminating such play when said clutch elements are disengaged throughthe spring loading of the second element affording an idling rotation ofthe shank.

3. The combination of claim 1 wherein a stop screw is provided on theend portion of said stud to prevent said first clutch element fromsliding off of said stud, said shank being provided with two spaced,cylindrical, peripheral faces and a connecting intermediate conicalperipheral face, and a bearing collar engaging one of said cylindricalfaces when the shank is in withdrawn position in the housing, saidbearing collar being disengaged from the cylindrical face as the shankis advanced from the housing and the conical face thereof passes throughthe bearing collar.

References Cited in the file of this patent UNITED STATES PATENTS748,018 Rowe Dec. 29, 1903 1,290,427 Velk Ian. 7, 1919 2,099,489 LambertNov. 16, 1937 2,184,779 Kiehne Dec. 26, 1939 FOREIGN PATENTS 650,454Germany Sept. 2, 1937

